Defrosting control in refrigeration system



July 14, 1959 G. MU FFLY DEFROSTING CONTROL IN REFRIGERATION SYSTEM Original Filed Feb. 4, 1949 2 Sheets-Sheet 1 July 14, 1959 G. MUFFLY 2,894,374

DEFROSTING CONTROL IN REFRIGERATIONSYSTEM original Filed Feb. 4, 1949 2 sheets-sheet 2 E E-J.

` JNVENToR. Za/fl? Muff@ VUnited States Patent O DEFROSTING CONTROL IN REFRIGERATION i SYSTEM Glenn Mulily, Springfield, Ohio 7 Claims. (Cl. 62--153) This application is a division of my copending application Serial Number 74,528 filed February 4, 1949, now Patent No. 2,709,343, issued May 31, 1955, and discloses an improved method of defrosting somewhat similar to that disclosed in my U. S. Patent No. 2,641,112 which issued June 9, 1953, but designed specifically for application to a household refrigerator whereas the patent above mentioned refers in particular to a commercial type of refrigerator for storing packages of frozen foods.

My Patent No. 2,641,112 discloses means for moving the evaporator relative to the insulated container for the frozen foods. The method employed herein is an improvement wherein means is provided for moving the insulated container in which frozen foods are stored instead of moving the evaporator for the purpose of preventing drippage of defrost water on the frozen foods while defrosting the evaporator.

My Patent 2,641,112 refers particularly to the welltype or top-opening freezer. In household refrigerators it is found desirable to employ a front-opening or drawer-type freezer. One disadvantage of the front-opening type of freezer is that when the door is opened room air flows into and out of the freezing compartment and deposits moisture on the walls, on the cooling surfaces of the freezer and on foods stored in the freezer. In the well-type or drawer-type freezer this spillage of cold air and entry of warm air, with the resulting condensation and freezing of moisture on the foods, is avoided, but most drawer-type freezers have employed non-insulated drawers located within insulated walls so that when a drawer is pulled out to afford access to the foods the contents of the drawer are not protected by insulation on the sides nor bottom. In the present disclosure I show a drawer which is insulated on four sides and the bottom so that when the drawer is pulled out for access tothe foods contained therein it is substantially as well protected from heat inltration through its front, back, sides and bottom as when the drawer is closed. Due to the fact that cold air is heavier than warm air, there is very little flow of warm air into the open drawer. Another factor which reduces the flow of air into and out of the drawer is found in the arrangement whereby the air surrounding the drawer is open to the room, thus the opening of the drawer does not produce a pumping effect on the air such as is ordinarly experienced in drawer-type cabinets.

The arrangement for defrosting the evaporator which cools the frozen food space is needed to overcomea serious objection raised by users of the present new models of household refrigerators in which two separately insulated and separately cooled compartments are provided, one for the storage of foods above 32 and one for the storage of frozen foods. It has become common practice to cool the warmer of these compartments through the medium of its liner. The freezing compartment is also sometimes cooled through the medium of its liner, but whether cooled in this manner or by means of an exposed evaporator it is impossible Ito properly defrost the freezing compartment without removing the frozen foods, which 2,894,374 YPatented July 14, 1959 are thus exposed to warmer air so that they start to thaw or at least collect moisture from ambient air. The present invention provides in addition to the nonfrosting main food compartment a convenient means for defrosting the frozen food compartment without disturbing or damaging the foods stored therein.

An object of this invention is to provide for defrosting the evaporator of a freezing compartment in a household refrigerator without disturbing the foods stored in this compartment.

Another object is to make better use of the usually wasted space below the main food compartment of a household refrigerator and in front of the condensing unit.

Still another object is to provide for automatic disposal of drip water resulting from the defrosting of the freezer evaporator.

Still another object is to provide against any drippage of defrost water or ice from the evaporator into the frozen food compartment.

A still further object is to provide for defrosting the freezer evaporator without interrupting the cooling of the main food compartment nor the making of ice.

An additional object is to provide for cooling the uppermost portion of the main food compartment to a somewhat higher temperature than the balance of the main food compartment.

Still another object is to provide a small shelf near the top of the main food compartment :for the storage of butter and other products in a somewhat higher temperature zone.

An additional object is to avoid the cooling of the top of the liner of the main food compartment, -th-us avoiding Ithe drippage of moisture from the top of the liner.

A still further object is to allow the use of a flat upper wall of the main food compartment liner so that bottles of maximum height may be placed on the uppermost fullwidth shelf at its extreme rear, thus providing for the storage of taller bottles at the rear of the shelf.

In the drawings:

Figure l is a vertical sectional View from the right side of a household refrigerator showing the frozen food compartment and its evaporator.

Figure 2 is a diagrammatic view of the refrigerating system and controls used in Figure l.

Figure 3 is a sectional view of the base of the cabinet showing the drawer slide and latch mechanism.

Figure 4 is a horizontal section of the drawer and cabinet base, showing the knob of the defrost control device.

Referring to Figure 1 which shows the household refrigerator 10 in vertical section, the main food space 12 is preferably cooled by non-frosting surfaces such as the rear wall 14 of the liner and is provided with shelves 15 and 15. The wall 14 is shown as a portion of the ice maker tank 16 in which ice is made and released by the method shown in several of my issued and copending applications, for example U. S. Patents Nos. 2,145,77 3, 2,145,774, 2,145,775, 2,145,777, 2,29l,826, 2,359,780, 2,368,675, 2,496,304, 2,544,394, 2,562,811, 2,572,508, 2,641,109, 2,656,689, and 2,672,016. The ice delivery spout 17 extends forward from the tank 16 and is provided with a hinger cover 17', as shown in my U. S. Patent 2,641,109. The evaporator 18 is employed to make and release ice, which is stored within the tank 16, thereby providing a supply of ice and the means for cooling the space 12. Y l

A second evaporator 20 is located below the insulated Wall 22 and arranged to operate at a temperature far below freezing so asV to cool the space 24 within the drawer 26 to the `desired temperature, which may bein the neighborhood of 0 F. Y

The cabinet is fitted with gaskets 30 which seal the the drawer 26 to the body of the cabinet. 'Ilhese gaskctsalso seal the side'walls of the'drawer to the cabinet so that when the drawer is closed it forms a substantially air-,tight compartment 24 for the storage` of frozen foods. This drawer ispreferably mounted on rollersand slides 'so-that vit can be pulled out almost its full depth as indicated in dotted lines Aat 26. VWhen in the open positionthe angular edge 32 assumes the position 32 below 'the angular bottom 38 of the cabinet wall so that any water dripping from the fin-type evaporator 20 will fall into the drip vpan 40 in which an absorbent pad 42 is shown. This pad extends upwardly so as to be contacted by room air which is drawn in through the opening 44 at the front of the base of the refrigerator, flows over the pan 40 and the pad 42, over'the motor-compressor unit 46 and then over the condenser 48. Such circulation of -air is induced lby the high temperature of the condenser hence it is not necessary to employ a fan and a -separate -motor to produce the desired air circulation.

While it is permissible to have the evaporators 18 and 20 operated at the same pressure and therefore at the Asame temperature it may, for economy of power consumption, be desired to operate the evaporator 18 at a higher vpressure and to continue its operation while the evaporator 20 is lbeing defrosted. I have shown various means for operating two evaporators at the same or ldifferent temperatures in my previous patents and copending applications.

Since the space 12 is cooled by nonfrosting surfaces, preferably by the liner 14, there will be only dew and no frost collected on the liner. The drain tube 49 includes a suitable trap and is arranged to conduct such condensate to the condenser 48, to the motor-compressor unit 46 or to the upwardly extending portion of the fabric 42.

The evaporator 20 is defrosted by means of hot gas from the condenser 48 and from the Compressor by the unit 46 while the drawer is in the open position 26. Such defrosting may be controlled by a solenoid valve or -valves. These valves will ordinarily rest in the position for normal refrigeration of evaporators 18 and 20 either simultaneously or separately according to the designers choice.

The drawer 26 must remain in its open position during the defrosting period, which may be or 10 minutes, but there is substantially no air flow into and out of the insulated drawer, hence no material loss of refrigeration nor warming of the frozen foods.

It will be noted that the front of the drawer 26 is higher than its rear wall so that the rear wal-l of the drawer passes below the evaporator when the drawer is opened but the crack between the drawer front and the fixed angular portion 28 of the refrigerator body is at a higher level than .the bottom edge of the ns of the evaporator 20. The evaporator 20 is located very close to the crack between the cabinet body and =the drawer. Air leaking in through this crack is light because of its temperature and moisture content, hence llows into contact with or very near to the evaporator before it makes contact with any of the food stored within the space 24. This results in cooling the air and condensing moisture from it before the air contacts any of the foods stored in the freezer drawer. While the fins cannot extend below the top of the back of the drawer, it will be noted that vthere are two gaskets 30 for this joint so that the air leakage is very small. These gaskets also seal the sides of the drawer to the insulated walls of the cabinet .and adjacent each such joint the evaporator 20 collects moisture in the form of frost, thus dehydrating the air before it makes contact with the foods stored in the drawer.

The motor-compressor unit 46 preferably has one small horizontal dimension, as in certain recently announced models, so that the front to back dimension of the condensing unit compartment can be minimized and a greater amount of space made available for the drawer 26. The condenser 48 may-optionally he located in 'the vertical flue 50 instead of in the angular position shown, thus allowing room for a still larger drawer 26. Optionally a fixed shield or wall may be provided between the drawer and the condensing unit to further reduce heat transfer from the condensing unit to lche drawer and its junction with the cabinet body.

Figure 2 shows electrical and refrigerant circuits suitable for use in Figure 1. 'The defrosting switch 52 is connected with a solenoid valve so as to start defrosting when the knob 54 of switch 52 is pulled outwardly. The defrosting switch 52 may be actuated automatically when the drawer 26 is pulled out to its extreme position 26', but this is not necessary and may not be considered desirable lbecause the 'user might wthdraw the drawer its full distance and inadvertently cause the evaporator 20 to defrost when not desired. I prefer to allow the user to actuate the knob S4 by hand when it is desired to defrost the evaporator 20 of the freezer. This vknob is preferably arranged so that it cannot 'be pulled out unless the drawer is open. In ordinary usage the drawer 26 is .not .open for more than a fraction of a minute at a time for taking food out or putting itin. 'During this time the evaporator 20 may be active but the resulting loss of refrigerating effect is negligible-and it prevents defrosting .at'inopportune times.

The switch mechanism 52 includes details as follows: Circuit from line conductor x68 is carried to the movable insulated contact member 7.0 by means of the flexible wire 72. This contact member is shown touching vthe Vtwo flexible contact members 74 .and 76. The contact member 74 is connected by means of the wire 78 withrthe switch which is arranged to close in response to a pressure or temperature rise in the evaporator 20, thereby energizing the motor of unit 46 with which line conductor 82 is permanently connected. The member 701is also touching the spring contact member 76 which is connected with the wire 84 leading to the ice maker switch 86 now assumed to Vbe open so that no current flows through the wire 88 to the solenoid 90, thus the valve 92 is at rest in `the position shown, which closes the inlet to `the ice maker .evaporator 18. In this position of the valve 92 high pressure vapor discharged fromth'e motor-compressor unit v46 flows through the tube '94 Vto the top of the condenser 48, being prevented by the closed valve 95 from entering the by-pass tube 96. Refrigerant liquefied in the condenser 48 ows through the liquid tube 98 and the restrictor 100 to the solenoid valve 92 which is in the position shown, thus causing the liquid refrigerant, now under low pressure to -flow through the tubes 102 `and 104 to the freezer evaporator 20. Refrigerant vapor leaving the evaporator 20 ows through the suction tube 106 back to the motor-compressor unit 46. It will be noted that the ycheck valve 108 prevents iigw of low-pressure refrigerant liquid to the evaporator So long as the freezer switch '80 remains closed and the ice maker'switch 86 remains open .operation will continue as above until the freezer evaporator drops toits cutout temperature or pressure at which time the switch 80 opens and the motor-compressor unit 46 stops. If, however, the ice maker switch 86 has closed in response to a rise of temperature of the bulb 110 before the freezer switch 80 reopens, the operation will be as follows: Current continues to flow through the motor of unit 46 as before although the closing of switch 86 has provided an additional path for parallel flow of current from the line 68 through wires 84 and `112 to the same motor. In addition the closing of ice maker switch 86 has provided a parallel path for current flow from the wire 84 through the wire 88 to the solenoid 90 which :is vconnected through the wire 114 tothe other conductor 82 of the line. The energizing of solenoid 90 causes the valve 92 to lift, thereby )diverting `flow of 1ow-pressure refrigerant liquid so that it now ows from the restrictor 100 to the tube 118 which feeds the ice maker evaporator 18 instead of through tubes 102 and 104 to evaporator 18. The mixture of refrigerant liquid and vapor leaving the evaporator 18 through the tube 120 lifts the check valve 108 and passes through the tube 104 to the freezer evaporator 20 from which vapor iiows through the tube 106 back to the suction side of the compressor in the unit 46. This results in cooling both the ice maker evaporator 18 and the freezer evaporator 20. If desired the check valve 108 may be weighted so that the evaporating pressure in the freezer evaporator 20 is lower than that in the ice maker evaporator 18, but this is not necessary if the main food space is cooled by the type of ice maker shown, which prevents any frost formation or undue dehydration of air in the main food space.

In the event that the freezer switch 80 reopens before the ice maker has been cooled to the temperature at which the switch 86 reopens, this operation will continue, but if the ice maker switch 86 reopens first the solenoid 90 will be deenergized and operation will continue as first described, cooling the freezer evaporator 20 only. The result is that the ice maker evaporator starts and stops operation in response to changes of temperature of the bulb 110, causing ice to be formed and released as described in earlier patents and vapplications of mine as noted above. This operation of the ice maker is the same as if there were no freezer evaporator 20. During operation of the ice maker evaporator 18, the evaporator 20 is also active, which may result in reducing the temperature of the evaporator 20 to a lower point than that at which its switch 80 opens, but this does no harm. If, however, the evaporator 20 requires further cooling after the ice maker evaporator 18 is cut out the cooling of evaporator 20 will continue until the switch 80 reopens. In the event that the ice maker tank 16 is full of oating ice down to the level at which this ice maintains the bulb 110 at a temperature below the cut-in point of the switch 86 and the temperature-pressure of the freezer evaporator 20 rises to the cut-in point of switch 80 the freezer may be cooled without cooling the ice maker. It is thus possible that a complete cycle of freezer cooling may occur without cooling the ice maker evaporator 18, but whenever the evaporator 18 is cooled the evaporator 20 is also cooled.

When the user desires to defrost the evaporator 20 she pulls the drawer 26 out to its full open position 26 and also pulls the knob 54 out to its position 54. This knob connects by means of the rod 122 with the switch arm 124 which is thereby moved to the position 124. This movement of the arm 124 rotates the shaft 126 on which it is mounted, thereby energizing the clock mechanism 128 which controls the return movement of the arm 124 so that it takes a predetermined length of time to travel from the position 124' to the position 124 at which point the arm 124 snaps back to the position shown by solid lines in Figure 2, wherecontact is remade with the members 74 and 76. At the time that the knob 54 is pulled outwardly Contact is first broken with the spring members 74 and 76 and then made with the spring contacts 130 and 132. The reclosing of the circuit from movable contact 70 to the spring contact 132 continues operation of the motor-compressor ,unit 46. At the same time the contact` made between the movable member 70 and the spring contact130 closes a circuit through the wire 134 and the solenoid 136 back to the other side of the line thereby causing the valve 95 to lift and allow high pressure refrigerant vapor to ow from the discharge tube 94 through the by-pass tube 96 to the freezer evaporator 20. This high pressure refrigerant vapor is prevented from entering the evaporator 18 by means of the check valve 108 and by the fact that the solenoid 90 is de-energized so that the valver92 closes the port leading to the tube 118. Thel hot refrigerant vapor causes defrosting of the evaporator 20 and returns at a reduced temperature through the suction tube 106 to the motor-compressor` unit 46, where it is Yreheated by the motor and by the compressor which recirculates it.

When the clock mechanism allows the contact arm 124 to snap from the position 124" to the solid line position shown in Figure 2, the circuit is reclosed through the switch 80, which is now closed because of the increased temperature and pressure of the evaporator 20 due to the defrosting operation, hence evaporator 20 immediately starts to cool when the timed defrosting operation has been completed. In the event that the ice maker switch 86 is closed at the time the defrosting operation is completed the evaporator 18 will also be cooled immediately after the defrosting operation is completed, but in any event the freezer evaporator 20 is always refrigerated immediately after defrosting. While the drawer is closed the switch closes before evaporator 20 reaches 32 F.

The operation of switch 52 by means of the knob 54 to initiate defrosting is preferably manual and may be accomplished upon opening of the drawer 26 which open drawer position provides that the defrost water from the evaporator 20 will fall into the pan 40 and not into the frozen food space 24. If desired a clock-actuated mechanism may be provided for opening the drawer 26 and moving the switch arm 124 at midnight or some convenient time. In any event it is preferred that automatic means be provided which upon closing of the drawer 26 will automatically stop the defrosting operation, for example, the front of the drawer 26 strikes the knob when in the position 54' and returns it to the position 54. In the absence of any automatic actuation of the switch 52 as provided by the clock mechanism 128 the termination of the defrosting operation is accomplished by the user pushing the drawer 26 to its closed position. In the event that the clock mechanism is used, but no automatic means is provided for reclosing the drawer the defrosting preferably would be done while the housewife is in the kitchen so that the open drawer serves as a reminder that it should be closed after the knob 54 has snapped back to its normal position. If the clock mechanism is not employed such open drawer reminds the user to reclose the drawer after sucient time has elapsed to complete the defrosting operation. As stated before, such closure of the drawer stops the defrosting.

An arrangement for automatically reclosing the drawer 26 when the defrosting operation is completed is seen in Figure 3. The drawer 26 is removably attached to a pair of angle irons which are slightly inclined and supported by the rollers 142, 144 and 146, which are mounted on the main body of the cabinet and preferably provided with ball or roller bearings. When the drawer is opened it is thus lifted slightly so that gravity tends to reclose the drawer. The spring-actuated pawl 148 engages the notch 150 in one of the angle members 140 thus normally retaining the drawer in its open position, but a slight push on the drawer or movement of the pawl 148 will cause the drawer to be reclosed by gravity. To reduce the push required to start the closing of the drawer and reduce friction so the drawer will close with less inclination of 140, the pawl 148 may be fitted with a `roller which engages the notch 150.

The pawl 14S will maintain the drawer 26 in its open position for removal of frozen foods since in opening the drawer the user will normally pull the drawer out to its full open position so that the pawl 148 engages the depression 150 in the track 140 in ywhich position the pawl is retained by the spring 154 with sufficient force to prevent the drawer from reclosing under the action of gravity.

Either mechanical or electrical means may be provided for momentarily Ireleasing the pawl 148 coincidentally with the return of switch 52 to its normal position, thus the user has only to open the drawer and pull out the knob 54 when she desires to defrost the freezer evaporator. Upon completion ofthe defrosting operation the switch returns to its normal position and the drawer recloses. Thisy insures against any damag'eto the frozen food resulting from the user Yforgetting to reclose the drawer and permits of defrosting during periods when the user is to be away subsequent to the initiation of the defrosting. v

One arrangement for accomplishing the' above result is illustrated in Figure 3. The switch mechanism 52 is herel assumed to be located on the cabinet body at the right-hand side of'the drawer below the right hand slide 140and the rollers with the rod 122 extending forward through the in-turned ilange 152 of the near side of the outercasing of the cabinet so that when the drawer is closed the flange portion of the drawer front (seen in Fig. 4) hides the knob 54 and pushes it to this position in thezevent that the knob was pulled out to the position 54T prior tothe closing of the drawer.

The pawl 148 is pivoted to the cabinet body by means of the pin 156 on which is alsorm'ounted the lever 158. This lever is free to move clockwise relative to the pawl against the force of spring 160, which normally urges it in counterclockwise direction until the shoulder 162 of the arm 158 strikes the shoulder 164 of the pawl. It is thus' seen that the arm 158 may be rotated clockwise against the action of the spring 160 without moving the pawl, but if the arm 158 is rotated counterclockwise for example upon movement of the rod 22 as will be ex plained below, its shoulder 162 and the shoulder 164 of the pawl cooperate to cause the pawl to be withdrawn fromthe recess 150 of the drawer slide, thus allowing the drawer to be reclosed by gravity. The form of the pawl148, the form of the recess 150 and the strength of the spring 154 are so related that suicient resistance is provided to drawer movement to prevent the drawer from reclosing, but this resistance is light enough to allow the drawer to reclose under the action of gravity if given a slight inward push or if the pawl is momentarily moved out of the recess 150.

As stated above, the rod 122 of the switch mechanism 52 extends rearwardly as shown in Figure 3 and is freely slidable in its supporting member 1644 attached to the cabinet body. This rod is provided with a collar 166 fixed thereto and is urged rearwardly (to the right in Figure 3) by the spring 168 which tends to move the knob from the position 54 to the position 54. This rod also carries a collar 170 which is xed to the rod so that it moves from the position 170 to the position 170' when the knob 54 is moved to the position 54. At the start of the defrosting period this collar will be located at 170 and will gradually approach the arm 158 as defrosting progresses. At the end of the defrosting period the rod 122 is suddenly released and the spring 168 moves it rearwardly (to the right in Fig. 3) so that the collar 170 engages the arm 158 and rotates the pawl from contact with the notch 150 in drawer guide 140. The collar 170 then passes beyond the reach of the arm 158, allowing the pawl to again Contact the drawer slide 140 after the drawer has started to move inwardly so that the pawl no longer engages the recess 150 in position to stop the drawer movement. It is thus seen that the ending of the defrost period 4results in the release of the drawer so that gra-fvity closes it. If desired, an air, -friction or spring stop may be provided to keep the drawer from slamming shut too violently.V

The pawl 148 may be held in' its releasing position for a few seconds to allow more time for the drawer to reclose or start reclosing if desired. This can be done by locating the collar 170 on the rod 122 so that it engages the lever 158 a few seconds before theV clock mechanism 128 releases the arm 124. The snap action which moves collar 170 `beyond the lever 158 to stop the defrosting and release the pawl will then occur when the drawer has closed to the point where' its front strikes the knob 54 and moves the rod 122 to the position shown by solidlinesvin Fig. 3. This arrangement also provides a cushioning eifectfor the .closing of the drawer as a certainamount of energy will be absorbed in moving the rod 122 prior to its release' 'by the clo`c k mechanism 128. This shockabsorbing effect can be increased by making the knob 54 of rubber or other compressible material. or by mounting a short coil spring, on the back of` the knob to strike the cabinet front at the end` of the inward movement of the rod 122. f

It should be noted that the drawer is heavily insulated on four sides and its bottom, thus the cold air in the drawer, being heavier than room air because of its low temperature, does not spill out of the drawer when open. An open top insulated containerof this type will keep frozen food in good condition for several hours even when open at the top and not refrigerated, assuming that the temperature of the frozen food contained therein was low enough to start with.

ln order to provide access to the controls andthe condensing unit the drawer 26 is preferably arranged for easy removal from ther cabinet. The drawer is provided on each side with a pair of sheet metal members 172 and 174 by means of which it is. supported on the longitudinal members 140. Oneset of said'members 172 and 174 for one side of the drawer is shown in Fig. 3. It will Ibe understood that the other set is a duplicate of the set shown. There is a slide on each; side of the drawer, but pawl 148 and Yassociated parts do not need to be duplicated. The slide 140 notV shown is a mirror equivalent of the' one shown. When thedrawer is pulled out to the position 26 it can be lifted off of; the slides 145. When replaced thereon the notches 176. in clips 172 and the outwardly turnedlugs 178 of the slides 140 provide for locking the slides in position on the drawer.

It will be understood that theclock mechanism 128 may actuate the switch arm 124k directly as shown in Figure 2 or may merely release the pawl 148 shown in Figure 3. In the later case the gravitational reclosing of the drawer 26 automatically returns the knob 54 to its normal position and stops the defrosting operation. lf it is desired to let the' clock stop the defrosting without reclosing the drawer, the rod.122 may be arranged to ao'tuate a signal instead of releasingY the pawl. If only the signal is actuated by the' clock, defrosting stops when the user reclosed the drawer.

In other of my copending applications, for instance in the one now Patent 2,641,109, I have shown control devices for selectively cooling the freezer evaporator or the 'ice' maker (main food space) evaporator, one at a time. Whereas the present disclosure showsV a system in which the freezer is at times separately cooled and is coincidentally cooled while' the warmer evaporator 18 is active, my previously disclosed methods maybe employed in connection with this' method for automatic de'- frosting of the freezer evaporator. Some of my control devices will allow for operation of the evaporatorY 18 while defros'ting evaporator 20. For instance the solenoid valve of Fig. 3 in my U.S. Patent 2,654,227, issued Oct. 6, 1953 could be used to' cause evaporator 20 to act as a condenser while evaporator 18 continues to' operate as an evaporator. v It will also be understood vthat either of the methods of defrostinga low-temperature evaporator by means of reversing the `actio'rt of the compressor or applying heat electrically to the' refrigerant, as disclosed in my U.S. Patent No. 2,641,112, issued June 9, 1953 may be employed in connection with the present disclosures. v A A In the last mentioned patent kof mine, theV evaporator is moved to a defrosting position whereas in the present application the insulated drawer i' sA moved for the purpose ofv defrostin'g; In' both cases, there is a' relative movement between the evaporator'and the" insulated container in which' foods arestored. Ihefe'arlie'r application is directed4 particularly lto cabinets' having a to'p opening' whereas #thev present application -refers `in particular to cabinets having two zones Vrefrigerated yto diierent' temperatures or to cabinets lhaving one or more insulated drawers for the storage of foods.

The pan 40 is made of suiicient depth to Lhold the maximum amount of water that can accumulate in the form of frost on the evaporator 20. The front of the drawer 26 is preferably made the full width of the cabinet whereas the width of the drawer is such as to allow space for the slides 140 and associated parts, 'thus the drawer front covers the knob 54 so that the drawer must be opened before the knob is pulled out.

While the drawer 26 is here shown as located in the lower portion 4of a household refrigerator cabinet, it will be undertsood that there may be several such drawers, as in a large locker cabinet and that the defrosting may be individually controlled for each drawer or defrosting initiated when a group of drawers are pulled out.

The heat for defrosting is herein shown as derived from high pressure refrigerant vapor, Ibu-t it will be understood that most of the features of this invention are attainable when electrical heat is used for defrosting, heat is obtained from water which has been warmed by a water cooled condenser or some other source of heat is provided either internally or externally of Ithe evaporator 20 to defrost i't. One -alternative method is to use electrical iheat `in a secondary refrigerant circuit as disclosed in my U.S. Patent Number 2,641,112. In the application just mentioned and in the present application, it will be noted that the evaporator is exposed to ambient air during the defrosting period, thus providing another source of heat for defrosting.

A separate signal may be provided to indicate that the defrosting operation is going on or that it has been completed. In the foregoing specication, it will be noted that the knob 54 `remains in the position 54 during the defrosting operation hence the automatic return of the knob to its normal position 54 is a signal that the defrosting operation has been completed while the location of the knob in the position of 54 is a signal that the defrosting operation is still going on.

I claim:

l. In a lrefrigerator, a drawer providing a food storage space, la refrigerating system including an evaporator for cooling said space, means for defrosting said evaporator while ysaid drawer is open, means so constructed and arranged as -to reclose said drawer, and means lfor retaining said drawer in its open position, the last said means being releasable in response to a slight manually applied force and also in response to completion of a defrosting period, to allow said drawer to be reclosed by the second said means, and control means for re starting and cooling of said space in synchronism with the reclosing of said drawer.

2. In a refrigerator, a drawer, an evaporator arranged to cool said drawer, means energized by the opening of said `drawer to Isupply power -for reclosing it, retaining means for lholding said drawer in its open position, means for defrosting said evaporator while the drawer is open, means 'for releasing said retaining means, to allow the drawer to reclose, and means responsive to the closing of `the drawer to stop the defrosting.

3. In a refrigerator, a plurality of compartments in said refrigerator, an insulated wall separating said compartments, a refrigerating system arranged to cool said compartments, said system including an evaporator arranged to operate at a temperature lower than 32 F. to cool one of Asaid compartments and an evaporator serving to cool the other of said compartments to a temperature above 32 F., a flow regulating device for liquid refrigerant feeding each of said evaporators, means forming a passage connecting said condenser with the lirst said evaporator and bypassing both said flow regulating devices, a valve normally closing said passage, a power source for opening said valve to cause defrosting of the rst said evaporator by supplying high pressure refrigerant thereto, means actuated simultaneously therewith to prevent flow of refrigerant through the second said evaporator, and a control device for restoring norm-al operation of said system in response to the completion of the defrosting operation.

4. In a refrigerator, a drawer enclosing a space for the storage of goods to be cooled, cooling means in said cabinet located above the closed position of said drawer to cool said space, defrosting means for said cooling means, means for starting said defrosting means when said drawer is in its open position, a control device operating to terminate the defrosting operation and thereby to reclose said drawer and restart the cooling of said space, and an energy source to actuate said control device.

5. In a refrigerating system, two evaporators, two pressure reducing devices feeding liquid refrigerant through one device only to one of said evaporators at a medium pressure and through both devices in series to the other evaporator at a lower pressure, a bypass valve arranged to connect the high side of said system with said lower pressure evaporator to bypass both said pressure reducing devices and said medium pressure evaporator for the purpose of defrosting said low pressure evaporator, the whole including means Iwhereby ow of refrigerant through said one evaporator is stopped during said defrosting, and self-actuating means for terminating said defrosting.

6. In a refrigerator, an insulated non-freezing storage space, a drawer forming an insulated freezing storage space, cooling means for said spaces, means operative when said drawer is open for defrosting the cooling means of the freezing storage space, drip drainage means for moisture condensed in said non-freezing space, drip collecting means for defrost water from the cooling means of said freezing space, evaporating means for disposal of both said moisture and said defrost water, and means actuated by the closing of said drawer for terminating the operation of said defrosting means.

7. In a refrigerator, a xed section enclosing a food storage space, a movable section enclosing a sub-freezing space, each said section having insulated walls, an evaporator located in said fixed section arranged to cool said movable section, drip catching means located below said movable section in position to catch water dripping from said evaporator when said movable section is moved from its normal position, means for applying artiiicial heat to said evaporator to defrost it, the last said means being operable only when said movable section is moved from said normal position, and a control mechanism arranged to stop said application of heat, and simultaneously allow said morvable section to move to its normal position and the cooling of said evaporator to restart at the end of a defrosting period.

References Cited in the le of this patent UNITED STATES PATENTS 1,228,067 Severance May 29, 1917 1,718,312 Shipley June 25, 1929 2,085,346 Vretman June 29, 1937 2,126,285 Schaaf Aug. 9, 1938 2,167,442 Alsing July 25, 1939 2,281,770 Hoesel May 5, 1942 2,423,386 Hubacker July 1, 1.947 2,430,141 Reeves Nov. 4, 1947 2,433,574 Newton Dec. 30, 1947 2,433,655 Zoppola Dec. 30, 1947 2,487,182 Richard Nov. 8, 1949 2,532,618 Henny Dec. 5, 1950 2,543,494 Hartman Feb. 27, 1951 2,612,026 Hansen et al Sept. 30, 1952 2,645,094 McCloy July 14, 1953 2,672,026 Murphy Mar. 16, 1954 2,709,343 Muiily May 31, 1955 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION latent No., 29895374. July 14, l959 Glenn Muffly It is hereby certified that error appears in the printed specification of' the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 55, after issued insert nu patents ma; .'olumn 3s line 3'?, for "Compressor by" read compressor of am.,

Signed and sealed this 16th day o February 196C@ (SEAL) Attest:

ROBERT C. WATSON K /BL H0 AXLINE Commissioner of Patents Attesting Ocer 

